Astronomy 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal F.2
Students were asked the following clicker question (Classroom Performance System, einstruction.com) in the middle of their learning cycle.
[0.3 points.] The Drake equation may predict that the Milky Way has many advanced technological civilizations. Which argument against this extremely optimistic result do you consider most valid?
(A) If there are supposed to be so many of them, then why aren't they here (yet)?
(B) Our advanced technological civilization on Earth arose due to an extraordinary number of highly unlikely coincidences and conditions.
(C) Since are no simple explanations as to why there would be zero contact from many other advanced technological civilizations (if they do exist), they do not exist.
(D) (More than one of the above arguments.)
Correct answer: (none; opinion only)
Each of these arguments was explained to the class before this question was asked. Item (A) is Fermi's Paradox; (B) is the Rare Earth Hypothesis; (C) is Occam's Razor (which is related to Fermi's Paradox). Students were instructed to choose the argument they considered the most valid, and only to select (D) if they were willing to talk about which of these arguments they considered equally valid.
Student responses
Section 4160
(A) : 5 students
(B) : 23 students
(C) : 5 students
(D) : 0 students
Section 5166
(A) : 4 students
(B) : 27 students
(C) : 12 students
(D) : 6 students
20080530
Astronomy quiz question: horizon problem
Astronomy 10 Quiz 12, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q12.4
[3.0 points.] Which one of the following statements best explains how inflation explains the "isotropy" of the universe today (equal amounts and same temperatures of cosmic background radiation coming from every direction)?
(A) Equal amounts of luminous matter and dark matter canceled each other out.
(B) The first generation of stars were pulled back apart into gaseous nebulae.
(C) Tiny quantum fluctuations in the universe expanded to become galaxy cluster formations.
(D) The curvature of the early universe expanded to become nearly flat.
(E) A very small part of an infinite universe increased to become the entire universe that we can see today.
Correct answer: (E)
This is the horizon problem of the cosmic background radiation, which is solved by the inflationary era. Since the universe is not old enough for the entire visible universe to have reached near thermal equilibrium, it must have experienced a brief, sudden expansion soon after recombination.
Student responses
Section 5166
(A) : 14 students
(B) : 5 students
(C) : 13 students
(D) : 10 students
(E) : 11 students
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q12.4
[3.0 points.] Which one of the following statements best explains how inflation explains the "isotropy" of the universe today (equal amounts and same temperatures of cosmic background radiation coming from every direction)?
(A) Equal amounts of luminous matter and dark matter canceled each other out.
(B) The first generation of stars were pulled back apart into gaseous nebulae.
(C) Tiny quantum fluctuations in the universe expanded to become galaxy cluster formations.
(D) The curvature of the early universe expanded to become nearly flat.
(E) A very small part of an infinite universe increased to become the entire universe that we can see today.
Correct answer: (E)
This is the horizon problem of the cosmic background radiation, which is solved by the inflationary era. Since the universe is not old enough for the entire visible universe to have reached near thermal equilibrium, it must have experienced a brief, sudden expansion soon after recombination.
Student responses
Section 5166
(A) : 14 students
(B) : 5 students
(C) : 13 students
(D) : 10 students
(E) : 11 students
20080529
Astronomy quiz question: Hubble's law
Astronomy 10 Quiz 12, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q12.2
[3.0 points.] Which one of the following statements best describes Hubble's law?
(A) Distant galaxies recede faster than nearby galaxies.
(B) Spacetime becomes more flat over time.
(C) Expansion must be followed by an equal and opposite contraction.
(D) There are equal amounts of dark matter and dark energy in the universe.
(E) The distances to other galaxies are farther away than expected.
Correct answer: (A)
Hubble's law correlates the recession speeds (v) of galaxies to their distances (d) from the Earth, where:
v = H*d.
Response (B) is related to the flatness problem of the cosmic background radiation, which is solved by the inflationary era. Response (C) is a mangled (but apparently convincing) version of Newton's third law: "For every action there must be an equal and opposite reaction." Response (E) is evidence (from type Ia supernovae) that the expansion of the universe is relatively recent.
Student responses
Section 5166
(A) : 36 students
(B) : 1 student
(C) : 6 students
(D) : 4 students
(E) : 2 students
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q12.2
[3.0 points.] Which one of the following statements best describes Hubble's law?
(A) Distant galaxies recede faster than nearby galaxies.
(B) Spacetime becomes more flat over time.
(C) Expansion must be followed by an equal and opposite contraction.
(D) There are equal amounts of dark matter and dark energy in the universe.
(E) The distances to other galaxies are farther away than expected.
Correct answer: (A)
Hubble's law correlates the recession speeds (v) of galaxies to their distances (d) from the Earth, where:
v = H*d.
Response (B) is related to the flatness problem of the cosmic background radiation, which is solved by the inflationary era. Response (C) is a mangled (but apparently convincing) version of Newton's third law: "For every action there must be an equal and opposite reaction." Response (E) is evidence (from type Ia supernovae) that the expansion of the universe is relatively recent.
Student responses
Section 5166
(A) : 36 students
(B) : 1 student
(C) : 6 students
(D) : 4 students
(E) : 2 students
20080528
Astronomy quiz question: universe inflation evidence
Astronomy 10 Quiz 12, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q12.4
[3.0 points.] Which one of the following choices best describes the evidence for the sudden early inflation of space in the universe?
(A) Stars in the inner and outer parts of the disk orbit the center of the Milky Way with the same speed.
(B) Each and every galaxy sees all other galaxies moving away from its location.
(C) Nearly equal amounts of cosmic background radiation are detected from all directions.
(D) Distant galaxies appear to be much younger than nearby galaxies.
(E) Type Ia supernovae in distant galaxies appear to be dimmer than expected from their redshifts.
Correct answer: (C)
Response (C) is the horizon problem of the cosmic background radiation, which may be explained by being a very small portion of the universe inflating suddenly and briefly to become the extent of the visible universe today. Response (A) is evidence for dark matter; response (B) is a reason why the expansion of the universe can be said to have no center; response (D) is a result of the finite speed of light ("lookback time"); while response (E) is evidence for the recent acceleration of the universe's expansion rate, caused by dark energy.
Student responses
Section 4160
(A) : 3 students
(B) : 4 students
(C) : 10 student
(D) : 0 students
(E) : 19 students
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q12.4
[3.0 points.] Which one of the following choices best describes the evidence for the sudden early inflation of space in the universe?
(A) Stars in the inner and outer parts of the disk orbit the center of the Milky Way with the same speed.
(B) Each and every galaxy sees all other galaxies moving away from its location.
(C) Nearly equal amounts of cosmic background radiation are detected from all directions.
(D) Distant galaxies appear to be much younger than nearby galaxies.
(E) Type Ia supernovae in distant galaxies appear to be dimmer than expected from their redshifts.
Correct answer: (C)
Response (C) is the horizon problem of the cosmic background radiation, which may be explained by being a very small portion of the universe inflating suddenly and briefly to become the extent of the visible universe today. Response (A) is evidence for dark matter; response (B) is a reason why the expansion of the universe can be said to have no center; response (D) is a result of the finite speed of light ("lookback time"); while response (E) is evidence for the recent acceleration of the universe's expansion rate, caused by dark energy.
Student responses
Section 4160
(A) : 3 students
(B) : 4 students
(C) : 10 student
(D) : 0 students
(E) : 19 students
20080527
Physics clicker question: blackbody versus silverbody
Physics 5A, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Conceptual Question 14.22
Students were asked the following clicker question (Classroom Performance System, einstruction.com) near the start of their learning cycle:
[0.6 participation points.] What should the outside of your jacket be like, in order to stay as warm as possible when hiking at night (in the dark)?
(A) Shiny, reflective.
(B) Black, matte.
(C) (It depends on how cold it is outside.)
(D) (It doesn't matter what type of jacket is worn outside in the dark.)
(E) (I'm lost, and don't know how to answer this.)
Sections 4987, 4988
(A) : 11 students
(B) : 5 students
(C) : 0 students
(D) : 15 students
(E) : 0 students
Correct answer: (A)
The rate of heat absorbed/emitted by an object depends on its emissivity: 1 for a perfect blackbody, and 0 for a perfect silverbody. While a blackbody will be an efficient absorber, it will also be a perfect emitter, which is desirable when cooling is an issue (e.g., car radiators, bottom tiles on the Space Shuttle), but at night, when heat loss by radiation needs to be minimized, a jacket approximating a silverbody would be better.
Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Conceptual Question 14.22
Students were asked the following clicker question (Classroom Performance System, einstruction.com) near the start of their learning cycle:
[0.6 participation points.] What should the outside of your jacket be like, in order to stay as warm as possible when hiking at night (in the dark)?
(A) Shiny, reflective.
(B) Black, matte.
(C) (It depends on how cold it is outside.)
(D) (It doesn't matter what type of jacket is worn outside in the dark.)
(E) (I'm lost, and don't know how to answer this.)
Sections 4987, 4988
(A) : 11 students
(B) : 5 students
(C) : 0 students
(D) : 15 students
(E) : 0 students
Correct answer: (A)
The rate of heat absorbed/emitted by an object depends on its emissivity: 1 for a perfect blackbody, and 0 for a perfect silverbody. While a blackbody will be an efficient absorber, it will also be a perfect emitter, which is desirable when cooling is an issue (e.g., car radiators, bottom tiles on the Space Shuttle), but at night, when heat loss by radiation needs to be minimized, a jacket approximating a silverbody would be better.
20080526
Physics clicker question: lava lamps
Physics 5A, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Conceptual Question 14.8
Students were asked the following clicker question (Classroom Performance System, einstruction.com) near the start of their learning cycle:
[0.6 participation points.] Why do wax droplets rise in a lava lamp after being heated in the base?
(A) Heat rises.
(B) Weight decreases.
(C) Density decreases.
(D) (I'm lost, and don't know how to answer this.)
Sections 4987, 4988
(A) : 9 students
(B) : 0 students
(C) : 21 students
(D) : 1 student
Correct answer: (C)
A lava lamp is an excellent demonstration of the principles of thermal convection. The light bulb at the bottom of the lava lamp heats the wax, which causes it to expand, decreasing in density. The expanded wax then rises, as it is now less dense than the fluid it is suspended in. Later after cooling at the top of the fluid, the wax will decrease in volume, increasing in density, and later sink.
"How lava lamps work"
http://home.howstuffworks.com/lava-lamp.htm
http://video.google.com/videoplay?docid=1145452462666090515
Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Conceptual Question 14.8
Students were asked the following clicker question (Classroom Performance System, einstruction.com) near the start of their learning cycle:
[0.6 participation points.] Why do wax droplets rise in a lava lamp after being heated in the base?
(A) Heat rises.
(B) Weight decreases.
(C) Density decreases.
(D) (I'm lost, and don't know how to answer this.)
Sections 4987, 4988
(A) : 9 students
(B) : 0 students
(C) : 21 students
(D) : 1 student
Correct answer: (C)
A lava lamp is an excellent demonstration of the principles of thermal convection. The light bulb at the bottom of the lava lamp heats the wax, which causes it to expand, decreasing in density. The expanded wax then rises, as it is now less dense than the fluid it is suspended in. Later after cooling at the top of the fluid, the wax will decrease in volume, increasing in density, and later sink.
"How lava lamps work"
http://home.howstuffworks.com/lava-lamp.htm
http://video.google.com/videoplay?docid=1145452462666090515
20080525
Physics clicker question: latent heat
Physics 5A, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Multiple-Choice Question 14.4
Students were asked the following clicker question (Classroom Performance System, einstruction.com) near the start of their learning cycle:
[0.6 participation points.] The heat capacity of a material undergoing a phase change (such as melting/freezing, or boiling/condensing) is typically:
(A) 0.
(B) ∞.
(C) some finite number.
(D) (Not enough information is given.)
(E) (I'm lost, and don't know how to answer this.)
Sections 4987, 4988
(A) : 8 students
(B) : 7 students
(C) : 12 students
(D) : 1 student
(E) : 0 students
Correct answer: (B)
The heat capacity is given by:
C = Q/delta(T).
When heat is put into (or taken from) a system undergoing a phase change, the temperature remains constant, and thus the denominator is zero, making the heat capacity infinite. Thus a system undergoing a phase change cannot have a defined heat capacity, as the heat goes into breaking or making bonds, instead of increasing/decreasing the amount of thermal energy in the system. Instead, the latent heat is defined:
L = Q/m,
where m is the amount of material undergoing a phase change.
Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Multiple-Choice Question 14.4
Students were asked the following clicker question (Classroom Performance System, einstruction.com) near the start of their learning cycle:
[0.6 participation points.] The heat capacity of a material undergoing a phase change (such as melting/freezing, or boiling/condensing) is typically:
(A) 0.
(B) ∞.
(C) some finite number.
(D) (Not enough information is given.)
(E) (I'm lost, and don't know how to answer this.)
Sections 4987, 4988
(A) : 8 students
(B) : 7 students
(C) : 12 students
(D) : 1 student
(E) : 0 students
Correct answer: (B)
The heat capacity is given by:
C = Q/delta(T).
When heat is put into (or taken from) a system undergoing a phase change, the temperature remains constant, and thus the denominator is zero, making the heat capacity infinite. Thus a system undergoing a phase change cannot have a defined heat capacity, as the heat goes into breaking or making bonds, instead of increasing/decreasing the amount of thermal energy in the system. Instead, the latent heat is defined:
L = Q/m,
where m is the amount of material undergoing a phase change.
20080524
Astronomy free-response question: Kepler's Third Law
Astronomy 10L Lab 12, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Students were asked the following open-ended question in an online pre-lab assignment, in order to prepare for a lab on determining the mass of Jupiter from the orbital periods and semi-major axes of its Galilean satellites:
Student responses
Sections 4161, 4162, 4163, 6544
Most responses were correct or nearly correct:
Cuesta College, San Luis Obispo, CA
Students were asked the following open-ended question in an online pre-lab assignment, in order to prepare for a lab on determining the mass of Jupiter from the orbital periods and semi-major axes of its Galilean satellites:
[0.2 points.] In your own words, describe Kepler's third law. (Graded for completion.)Students were graded for any non-blank response that demonstrates a serious (or not-so serious) attempt at completing the assignment.
Student responses
Sections 4161, 4162, 4163, 6544
Most responses were correct or nearly correct:
"The squares of the orbital periods of planets are directly proportional to the cubes of the semi-major axis of the orbits."A number of responses discussed Kepler's first or second laws, Newton's laws of motion, or even laws of cooling:
--K. D.
"The farther a planet is away from the sun, the longer time it will take for that planet to orbit the sun once."
--C. R.
"Which one was that... is that the one where all planets... I give up. The first one is about ellipses,... it has something to do with how long planets take to orbit the sun, I think."
--A. R. (1)
"the close ones go faster just like michelle kwan."
--M. M.
"Equal distances are covered in equal times."Some responses went in apparently just for kicks (but still get full "completion" credit):
--A. B.
"It represents the motion of planets around the sun."
--E. D.
"An object in motion will remain in motion."
--J. A.
"Area to volume ratio! yea."
--S. M.
"its a law that kelper made."
--A. R. (2)
"My words dont do this law Justice."
--R. G.
"Drawin' a blank."
--B. M.
"Keplers third law is never talk about keplers first two laws."
--D. F.
20080523
Planetary rings: tire debris
Photoshop Phriday: World Without Wheels, by Cuddly Dansomethingawful.com
May 16, 2008
Oddly enough, the plane of the ring does not coincide with the equatorial plane of the Earth.
Astronomy quiz question: globular cluster star formation
Astronomy 10 Quiz 11, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q11.5
[3.0 points.] Which one of the following statements best explains why there are no young stars in the halo clusters of the Milky Way?
(A) There are no longer enough heavy elements remaining in the halo.
(B) There are not enough gravitational forces in the halo for new stars to form.
(C) The dark matter in the halo prevents new stars from forming there.
(D) All of the metal-rich stars in the halo clusters have already become metal-poor stars.
(E) All of the interstellar hydrogen in the halo moved into the disk.
Correct answer: (E)
According to the monolithic formation theory of the Milky Way, the gas and dust in our galaxy was originally spherically shaped. Then as the first-generation stars of the globular clusters formed, hydrogen in the Milky Way gradually collapsed into the thin disk structure that it has today. Thus no new stars can form in the relatively empty spherical halo that surrounds the flattened Milky Way.
Student responses
Section 5166
(A) : 3 students
(B) : 16 students
(C) : 6 students
(D) : 7 students
(E) : 18 students
Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal Q11.5
[3.0 points.] Which one of the following statements best explains why there are no young stars in the halo clusters of the Milky Way?
(A) There are no longer enough heavy elements remaining in the halo.
(B) There are not enough gravitational forces in the halo for new stars to form.
(C) The dark matter in the halo prevents new stars from forming there.
(D) All of the metal-rich stars in the halo clusters have already become metal-poor stars.
(E) All of the interstellar hydrogen in the halo moved into the disk.
Correct answer: (E)
According to the monolithic formation theory of the Milky Way, the gas and dust in our galaxy was originally spherically shaped. Then as the first-generation stars of the globular clusters formed, hydrogen in the Milky Way gradually collapsed into the thin disk structure that it has today. Thus no new stars can form in the relatively empty spherical halo that surrounds the flattened Milky Way.
Student responses
Section 5166
(A) : 3 students
(B) : 16 students
(C) : 6 students
(D) : 7 students
(E) : 18 students
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